Persons who are prone to dental caries are inadequately served by today""s preventive dental care. Lack of educational awareness in dental care and lack of odontological awareness in education has meant that there are insufficient aids and working methods to help these persons effectively.
The invention relates to a system that solves the problem according to the pre-characterising part of claim 1.
Dental caries is the world""s most common multifactoral disease but also one that it is possible to avoid by means of personal care measures for those who have adequate knowledge of the disease process and their own susceptibility to disease at a given time. This is because the risk of caries varies between individuals and in the individual over time. There is therefore no single method of prevention that will help all individuals every time.
If dental care personnel had the knowledge, capability and incentive to teach the patient how to proceed at any given time in order to counteract caries, the need for dentists would be drastically reduced. A corresponding effect would be achieved if skilled teachers had the odontological training that is required. So the aids which the dental hygienist needs in order to train patients are not developed for this. The lack of educationally sound aids and working methods is a problem in dental care.
It is well known that fluoride prevents dental caries and that the most important mechanism is the formation of fluorapatite on the tooth surface in connection with a reduction of the pH level to a given interval. It is also known that fluoride does not have an adequate protective effect in persons highly susceptible to caries, despite the fact that a large number of studies have been carried out with systems of fluoride administration currently in use. The most important source of fluoride is reckoned to be toothpaste.
That fluoride treatments fail is due to the fact that the dental hygienist does not take into consideration that dental caries is a multifactoral disease. It is not sufficient, as at present, to try to solve the problem of caries simply with large doses of fluoride. A factor of at least equal importance is the pH-value in the films on the tooth surface.
After eating carbohydrates the caries process causes a reduction of the pH value of the tooth films from a normal value of approximately 7.0-7.5. After a time that varies according to the individual the pH value rises again to the normal value. The curve described by the pH value during this time is known as Stephan""s curve. Important factors that affect its appearance are partly the concentration of acid-producing microorganisms in the tooth films, including streptococci mutans, which end to reduce the pH value. Buffer substances, which are present in normal saliva. endeavour to counteract the reduction and to increase the pH value after a reduction. The most important buffering systems are founded on the presence of bicarbonates and phosphates in the saliva, but proteins, urea and mucoid substances have buffering characteristics.
An individual may have a number of combinations of bacteria content and buffering capacity and many Stephan curves with different appearance therefore exist. Extreme variants include, on the one hand, a pH reduction from the normal value of 7.0, by about one pH unit for a few minutes, and on the other a large reduction to values of less than 4.0 for up to two hours. Owing to a number of circumstances all these variants can, in theory, occur in each individual from time to time.
Despite the great significance of buffering for the appearance of the Stephan curve, clinical studies have only been able to show a slightly negative correlation between the buffering capacity of the saliva and caries in a normal population. The reason is that there are many other factors that affect the development of caries, among other things the presence of fluoride, good oral hygiene and good discipline with regard to sugar, all of which reduce the strength of the connection. In clinical studies the connection was so weak that simply measuring the strength of the buffering is not regarded as adequate for assessing the risk of caries in an individual. In persons with a high bacteria content on the tooth surface the correlation is greater and is due to the fact that many of these persons have a large pH reduction after eating, which increases the prophylactic importance of the pH-increasing buffering.
It is generally assumed that the correlation is linear and that persons with the highest buffering capacity should run the least risk of caries. In one (unpublished) clinical study of 96 teenagers with high acid-producing content of streptococci mutans in the saliva we found, however, that persons with medium buffering had least caries of all, including those who had better buffering (Table 1).
The high standard deviations indicate that a few individuals had developed great caries attack in each group. Note that this is a cross-sectional study and the result shows the accumulated quantity of caries attack over several years. It is highly probable that the buffering capacity of many participants has changed during the period (Table 2), which explains why certain persons with high buffering values at present ( greater than 5.5) have a large amount of caries damage. All those taking part have been exposed to fluoride rinses every 14th day from the age of 7 and have used fluoride toothpaste regularly.
These observations indicate that the intermediate group run a lower risk of caries than the group with an inferior or superior buffering capacity in a material that is exposed to fluoride.
Table 2 shows that the proportion of persons who had low buffering capacity was halved during the first six months. After a further year the proportion was the same at the start.
In the light of this there are good reasons to assume that it is a combination of fluoride and exactly the right buffering capacity which gave the intermediate group in Table 1 less caries than the high-buffering group.
From a practical point of view the result in Table 1 indicates that the risk of caries should be reduced if the content of buffering substances in the low buffering group could be increased, whilst a lowering of this in the high-buffering group should reduce caries in that group.
Fluoride Reduces the Critical pH Level
If there is fluoride deficiency in the mouth, the tooth enamel looses minerals when the pH value has dropped to less than 5.5 after eating. A low-buffering person very often has a lower pH value after eating than a person with higher buffering. If fluoride is present the critical limit is reduced to 4.5. In the pH interval 4.5-5.5 the enamel is certainly demineralised first, but afterwards a precipitation of fluorapatite occurs, which compensates for the mineral loss and forms a surface that has high resistance to the low pH values.
Moderate pH Fall Promotes Formation of Fluoranatite
Above pH 5.5 the formation of fluorapatite is a slow process. pH is often at this level in persons who belong to the high buffering group. If the pH on their tooth surfaces is reduced from 7.0 to 5.0, the rate of formation of fluorapatite rises 20 times (ref. 2).
Large pH Fall Prevents Formation of Fluorapatite
If the pH falls below 4.5 a constant mineral loss occurs and fluorapatite is not formed without the presence of a very high fluoride concentration and the longer this low pH value exists, the greater the mineral loss becomes. Persons in the low-buffering group in our study develop low pH values more frequently than the other groups, which explains why they get so much caries.
It can be demonstrated that, after eating, certain persons develop pH values as low as or lower than 4.0 in tooth films (ref. 3). In some of these persons the pH value returns to the normal 7.0 with a few minutes (ref. 4). whilst others may have a mineral-dissolving low pH value for up to two hours (ref. 3). When the pH value increases from 4.0 to 5.0, the mineral loss is greatly reduced even at very low fluoride concentrations (ref. 1). For persons who usually develop low pH values in tooth films after eating, such a raising of the pH value following each consumption of food gives a good fluoride protection with a significantly lower quantity of fluoride than is required if fluoride alone is used, without pH adjustment. According to ten Cate and Duijsters 5 ppm should be required at pH 4.0, but at pH 5.0 only 0.05 ppm is required in order to achieve the same effect, that is to say raising the pH value by one unit should reduce the fluoride requirement to one hundredth.
In the light of this it is probable that the intermediate-buffering group in our study (Table 1) forms fluorapatite better than the high-buffering group and considerably better than the low-buffering group, due to the fact that the optimum pH value for apatite formation occurs more often than in other groups.
pH Correction Required
In the light of this, persons who develop pH values that lie outside the interval 4.4-5.5 ought to be treated with orally administered substances that bring the pH value into this interval, increasing the formation of fluorapatite and reducing caries.
Identification Problem
The problem is to identify these persons. None of the tests that are currently used manage this. Although the buffering capacity of the saliva provides a guide, it tells us nothing about the occurrence of streptococci mutans, which has an influence on the appearance of the Stephan""s curve. Furthermore it provides no information on the buffering, which occurs in the tooth films. Nor does the occurrence of streptococci mutans provide adequate information, since its tells us nothing about the buffering. Even a combination of these two tests does not provide sufficiently accurate information on what happens in the plaque after eating.
pH-influencing Toothpastes
In Sweden toothpastes with a pH value of 5.5 are to be found. In other countries there are quite a few with even lower pH. A low pH value in toothpaste is reckoned to produce a suitable lowering of a high pH value in tooth films and thereby to increase the formation of fluorapatite. The idea is logical but assumes that the pH-reducing toothpaste is not used by persons prone to caries, who have just consumed carbohydrates. In these people the toothpaste rather tends to reinforce the normal pH reduction that occurs after eating and risks reducing pH too far, that is to say below 4.5 over a prolonged period, when mineral is lost without any formation of fluorapatite to compensate. In practice, therefore, acid toothpastes increase the risk of caries in these persons. Acid toothpaste must only be used by persons who are shown to experience a large or short-term pH fall after eating, for example high-buffering persons.
There is a problem that persons who develop low pH levels after eating sometimes use toothpaste with a low pH value.
Some Toothpastes Have a pH Value That Is Higher Than the Normal pH Value of the Saliva
A high pH value in toothpaste is reckoned to produce a rise in a pH value that is too low, thereby interrupting the caries process and promoting the formation of fluorapatite, but if it is used by persons who have an insignificant or moderate fall in the pH value after eating there is a great risk that the pH value will be increased to a level at which only insignificant quantities of fluorapatite are formed, for example the high-buffering group in our study. Due to the small quantity of acid-resistant fluorapatite their preparedness for changes in the risk of caries is therefore poor. This does not matter as long as a high pH level is maintained after eating. But the saliva mechanisms that affect the appearance of the Stephan""s curve are unfortunately changed over time in certain individuals (Table 2). This can means that persons who once had optimum protection against caries owing to the formation of fluorapatite may later experience a pH reduction that goes below 4.5, thereby rapidly increasing the development of caries.
A high pH value in toothpaste must therefore only be used by persons who are shown to experience a large, long-lasting fall in pH level after eating.
There is a problem that persons who for a short time return to a high pH level after eating sometimes use toothpaste with a high pH value.
Acid and basic toothpastes on sale do not inform the public of these risks. Another deficiency of these toothpastes is that the purchaser does not know whether the pH change they initiate leads to optimum conditions for the formation of fluorapatite. There is no indication, for example, whether one or two cm are to be used. Is one to se a single or a double dose of the substance that affects the pH level? The wrong choice can lead to a minimal formation of fluorapatite.
The reason for these deficiencies is that there is no practical measuring technique that shows the individual which toothpaste gives the best fluorapatite production and hence the optimum protection against caries in a particular case. This is a problem.
An American patent filed in 1978 (U.S. Pat. No. 4,108,980) describes a pH reducing composition with fluoride and a pH-increasing composition. The patent does not indicate, however, on which patients these compositions are to be used or how these are to be identified. The patent claim only covers the reduction of a pH level that is too high with a view to increasing the formation of fluorapatite. The method and the pharmaceutical preparations can not be used in the manner prescribed for persons who, when being treated, have a low pH value on the tooth surface. This would then, on the one hand, counteract the formation of fluorapatite, and on the other would increase the demineralisation, both of which are contrary to the aim of the patent""s application. Nor can the pharmaceutical preparations specified by the patent be used by the general public.
The object of the invention is to solve the above-mentioned problem. The solution provides dental care personnel with an educationally well though-out system of working with adequate aids, which in turn helps the patients firstly to understand their risk of caries and secondly to take the measure that is currently required in order to prevent caries.